What to consider when sealing expansion joints or movement joints
Movement of the joint
The biggest challenge is the different movement coefficients of the various materials that the joint is made from. For example, gypsum, concrete and aluminium all expand and contract at different rates. The sealant should not only strongly adhere with different substrates, but also accommodate different degrees of movement for the materials it joins.Similarly, expansion joints in floors need to be able to withstand the pressure from high levels of foot traffic and constant movement and weight, without their functionality being affected.
Material and finish
The desired look of the surface or finish also matters. Building facades need to look immaculate without staining or streaking, despite the weather changes and precipitation they face.
Plus, with many applications featuring different materials, it’s important to know how the material will affect your decision in choosing the right expansion joint sealant.
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Building regulations and safety
Building regulations and safety will impact which sealant you need to use. For example, certain materials must comply with relevant legislation, such as the Construction Products regulations or Approved Document B.For internal and external expansion joints which need to be fire retardant, we recommend using a sealant that is not only highly flexible but also offers passive fire resistance.
Our Bostik FP403 Fireseal Hybrid sealant is a one-component, fire resistant sealant, suitable for sealing linear joints up to 4 hours and offers a movement accommodation of 25%. It's perfect for both vertical and horizontal joints in walls, floors, ceilings, metal frames and more.
Before choosing which sealant to use, we strongly recommend that you check the integrity and insulation requirements for your project.
External expansion joints
Expansion joints in facades and floors consist of connections between exterior building elements. You need a sealant that can weather environmental stress and still offer a great finish. At Bostik we offer a wide range of products that are suitable for expansion joints.
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How to seal an expansion or movement joint
There are several kinds of expansion and movement joints. Since these joints should be able to absorb a lot of stress, they should be correctly designed. We advise that you contact our in-house experts if you have any doubts or queries.The durability of a movement joint depends on three factors: pre-treatment, choosing the optimal product, and correct application.
- Check the substrates of your tiles or other materials before purchasing your sealants. Since a movement or expansion joint will probably undergo a lot of movement and pressure, using the most optimal product will ensure it stays durable and doesn’t crack. For instance, pure silicone sealants are very durable and can withstand UV exposure.
- Before applying any sealant, ensure the surface is clean, dust free and dry.
- The depth and width of joints should be in line with the movement coefficient of the building substrates.
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